1. Field of the Invention
The present invention relates to a hydraulic piping structure for connecting a hydraulic pump of a crawler-type hydraulic driving vehicle and a drawer driving hydraulic motor.
2. Description of the Related Art
Japanese Patent Laid-Open No. 202150/1997 discloses one example of a hydraulic piping structure for connecting a hydraulic pump arranged within a vehicle body frame, and a crawler driving hydraulic motor arranged in each of longitudinal end portions of a pair of track frames arranged on left-hand and right-hand sides of the vehicle body frame in a conventional crawler-type hydraulic driving wheel such as a bulldozer.
FIG. 6 is a side view of a hydraulic hose piping structure of a crawler-type travel device disclosed in Japanese Patent Laid-Open No. 202150/1997. FIG. 7 is a plan view of the hydraulic hose piping structure. In FIGS. 6 and 7, a hydraulic pump 10 is arranged inside a vehicle body frame 1. Left-hand and right-hand track frames 4L, 4R (4R is omitted in these figures) are attached to both left-hand and right-hand sides of the vehicle body frame 1 in parallel with forward and backward directions. Left-hand and right-hand crawler driving hydraulic motors 11L, 11R are respectively attached to one-end portions of the left-hand and right-hand track frames 4L, 4R in the forward and backward directions. The hydraulic pump 10 and the left-hand and right-hand crawler driving hydraulic motors 11L, 11R are connected by four hydraulic pipings 30a, 30b, 30c, 30d. Each of hydraulic pipings 30a, 30b is inserted into a communication hole 31 arranged in a side face portion of the vehicle body frame 1 and is piped. Each of hydraulic pipings 30c, 30d is inserted into a guide rod 32 arranged in a lower portion of the vehicle body frame 1 and is piped. A connection plate 33 is arranged above passing positions of the hydraulic pipings 30a, 30b, 30c, 30d to protect these hydraulic pipings.
However, there are the following problems in the above construction of the prior art.
(1) The communication hole 31 is bored on each of left-hand and right-hand side faces of the vehicle body frame 1 in its longitudinal direction (i.e., the forward and backward directions) to pipe the hydraulic pipings 30a, 30b. Therefore, strength of the vehicle body frame 1 is reduced. Accordingly, it is necessary to thicken a plate thickness and arrange a reinforcing member to reinforce the vehicle body frame 1.
(2) The hydraulic pipings 30a, 30b, 30c, 30d extend through the left-hand and right-hand side faces of the vehicle body frame 1 from its inside and are taken out to the exterior, and are connected to the left-hand and right-hand crawler driving hydraulic motors 11L, 11R. Therefore, a portion of the hydraulic pipings exposed to the exterior of the vehicle body frame 1 is lengthened, and upper and side portions of the hydraulic pipings in E-portions are exposed to the exterior as shown in FIG. 7, and a lower portion of the hydraulic pipings is also exposed as shown in FIG. 6. Accordingly, there is a fear that the hydraulic pipings easily come in contact with an external rock, an obstacle, etc. and are damaged.